Abstract [en]

The deformation and damage mechanisms arising during thermomechanical fatigue (TMF) of the polycrystalline superalloy IN792 have been investigated. The TMF cycles used in this study are in-phase (IP) and out-of-phase (OP). The minimum temperature used in all TMF-tests is 100 °C while the maximum temperature is 750 °C in the IP TMF-tests and 850° or 950 °C in the OP TMF-tests. Most cracks have propagated transgranularly through the material and this holds for all temperatures used in this study. In all tests, the cracks have initiated and propagated in locations where deformation structures such as deformation bands have formed in the material. In the temperature interval 750°-850 °C, twins are formed in both IP and OP TMF-tests and this behaviour is observed to be further enhanced close to a crack. Twins are to a significantly lesser extent observed for tests with a higher (950 °C) maximum temperature. Recrystallization at grain boundaries, around particles and within the deformation structures have occurred in the OP TMF-tests with a maximum temperature of 850° and 950 °C and this is more apparent for the higher temperature.